Research on motor cooling process of centrifugal refrigeration compressor with gas bearings

Abstract

Centrifugal refrigeration compressor with gas bearings is an important development direction for the water chiller. The high-speed and compact structure leads to worse heat dissipation conditions for the motor and cooling it with refrigerant directly is an effective method. In this paper, the flow field of the refrigerant and the temperature distribution of the motor under different operating conditions and structural parameters are simulated. The results show that the highest temperature point of the motor is at the central position, and the stator winding temperature is much lower than the permanent magnet. The cooling process is related to the inlet pressure, inlet dryness, back pressure, and the structure of the cooling passage. Increasing the inlet pressure and decreasing the back pressure will reduce the temperature of the stator winding and the permanent magnet in the motor. The inlet dryness will influence the windage loss change obviously so that the temperature change trend of the stator winding and permanent magnet is different, the temperature variation range of winding and the permanent magnet is 16 °C and 40 °C respectively. Increasing the inlet diameter, outlet diameter, and injection orifice diameter will reduce the motor temperature, but the temperature changes slightly after it reaches a certain value. In the selected adjustment range, the outlet diameter has the greatest influence on the motor temperature, and the temperature variation ranges of winding and permanent magnet are 28 °C and 120 °C respectively.